Many circuits currently use discrete components and/or integrated circuits (ICs) that may be produced with different types of processing and materials. Some of the different types of processing and materials may include complimentary-metal-oxide-semiconductor (CMOS), gallium-arsenide (GaAs), lithium tantalate (LiTaO3), and silicon-germanium (SiGe). Traditionally many of these devices have been assembled and interconnected on ceramic or organic interconnect devices that have traces to interconnect the various ICs and/or passives. The resulting interconnected circuit is then packaged as a single component.
FIG. 1 is a known example of interconnecting various ICs with an interconnect device. Passive substrate 110 represents traditional interconnect devices, typically organic material (e.g., FR4) or ceramics. Passive substrate 110 is passive because it has no circuit functionality except to assemble and interconnect the various circuit components. All circuit functionality, such as processing, manipulating, affecting, etc., signals in the circuit is performed in the various circuit elements assembled on top of passive substrate 110. Thus, the ICs, switches, and passives shown in FIG. 1 are the functional circuit elements. The main advantage to using passive substrate 110 is that it is relatively inexpensive, generally only requiring that contact pads and interconnect traces be manufactured onto passive substrate 110. The circuit components are then bonded or soldered to passive substrate 110. Thus, various ICs of potentially many disparate processing technologies and/or procedures can all be packaged as a single component.
Examples of various circuit elements include RLC 120, which represents discrete passive components such as resistors, inductors, and capacitors, and filters created with such passive components. These components are used to passively process signals occurring in system 100. ICs of differing processing technologies and materials are also shown as CMOS 130, SiGe 140, LiTaO3 150, and switch 160.
CMOS 130 represents ICs that are made with complimentary metal (or other conductor) oxide semiconductor (e.g., silicon) processing. SiGe 140 represents ICs that are manufactured with silicon germanium processing. Because of the differences in processing of these two technologies, processing of circuits using these different technologies occurs on different substrates and interconnecting occurs on an interconnect device such as passive substrate 110. The use of different types of circuits made with the different technologies is assumed to be well understood in the art, and consequently will not be discussed herein. Note that the interconnecting of ICs 130, 140, 150, and 160 may be performed by flip-chipping the IC and bonding to bumps, or by the use of wire bonds, as shown with SiGe 140. Additionally, the various ICs shown could be bare die rather than packaged.
LiTaO3 150 represents devices processed on a lithium tantalite substrate, which is a boutique processing technology that is traditionally used with surface acoustic wave (SAW) filters. Switch 160 is shown as one traditional element that is processed using GaAs to provide fast switching, for example, switches in radio frequency (RF) devices.
Input/Outputs 170 are used in packaging system 100. Input/Outputs 170 pads or bumps use vias through passive substrate 110 to provide interconnection to the circuitry of system 100 to the packaging of system 100. The interconnection to the packaging may be through wire bonding or metal traces connecting to the packaging pins.
Despite the inexpensive interconnect provided by passive substrate 110, there may be undesired expenses in the processing of the various ICs shown in FIG. 1. For example, many ICs use boutique processing technologies such at LiTaO3 or GaAs that can be significantly more costly than silicon-based processing. However, use of these processes has been necessary to achieve the desired performance. Integrating these components made with boutique processes with strictly silicon-based components has proven costly.
Another example of the expense in traditional practice is that many circuits require the use of resistors, capacitors, inductors, and passive filters. These components may be integrated directly on the IC, or they may be discrete components, such as LTCC (low temperature co-fired ceramic) devices, that require bonding to passive substrate 110. However, there are costs associated with using discrete passive components, as well as directly integrating passives on modern ICs manufactured with high precision (e.g., 90 nm) processing. The higher precision processing is used to scale ICs with active devices such as transistors, which are typically scaleable. The increased cost of manufacturing may be justified by the increases in performance of the resulting devices. However, higher precision processing does little or nothing to increase performance of components such as the passives that do not scale. Also, for devices such as voltage regulation circuits and certain sensors, non-high-end processing is also perfectly viable for producing circuit elements of acceptable performance, making the use of high-end processing for such devices wasteful. Thus, integrating these devices on ICs consisting of scaleable active device with modern processing techniques is wasteful of processing costs as well as valuable die real estate.